1. Field of the Invention
The present invention relates to a piping structure for a brake hose for a motorcycle.
2. Description of the Relevant Art
Brake hoses for motorcycles are used in brake devices, and are laid in order to absorb vertical movement of a wheel with respect to a fixed position on a motorcycle body. One such brake hose structure is disclosed in Japanese Patent No. 2506358 entitled xe2x80x9cHydraulic Brake Device for Rear Wheel in a Motor Vehicle such as a Motorcycle.xe2x80x9d As shown in FIG. 9, about one turn of a brake pipe 25 is wound on a front end of a rear arm 8, in accordance with the background art.
However, with about one turn of the brake pipe 25 wound on the rear arm 8, a brake hose tends to hit the rear arm 8. Particularly, the brake hose is liable to be worn by intensive vibrations and large vertical movement of the rear wheel on an off-road vehicle that often runs on rough terrain.
If a bend in the brake hose is placed on the rear arm 8, then the bend is positioned closely to a rear portion of the engine, resulting in reduced leeway for the shape of the rear portion of the engine.
It is therefore an object of the present invention to provide a piping structure for a brake hose for a motorcycle, which allows increased leeway for the shape of the rear portion of the engine of the motorcycle.
In order to attain the object described above, the present invention provides a piping structure for a brake hose for a motorcycle. The motorcycle has a master cylinder for a rear disc brake that is mounted on a motorcycle body forwardly of a rear fork. A brake hose extends from the master cylinder and is directed forwardly, then turns back, forming a first U-shaped portion. The first U-shaped portion extends along an upper surface of the rear fork, and connects to a brake caliper of a rear wheel. The brake hose has a portion fixed to the rear fork at a location that is closer to the brake caliper than the first U-shaped portion. A portion of the brake hose that is closer to the brake caliper than the fixed portion is curved into a second U-shaped portion. The second U-shaped portion is convex toward the center of the motorcycle body. The brake hose is held near the second U-shaped portion by a first hose guide which limits the brake hose against upward movement, but allows the brake hose to move parallel to the surface of the rear fork.
The first U-shaped portion is formed in the brake hose, and the portion of the brake hose that is closer to the brake caliper than the first U-shaped portion is fixed to the rear fork. The first U-shaped portion absorbs changes in the brake hose that are caused as the rear fork moves vertically.
The second U-shaped portion is formed in the brake hose more closely to the brake caliper than the fixed portion of the brake hose. The brake hose is held by the first hose guide near the second U-shaped portion. The second U-shaped portion absorbs axial movement of the brake hose.
Since an ability to absorb changes in the brake hose is distributed between the first U-shaped portion and the second U-shaped portion, the space occupied by the area where the first U-shaped portion is arranged can be reduced. Therefore, the leeway for the shape of the rear portion of the engine is increased.
According to the present invention, the piping structure is characterized in that the first hose guide is mounted on a cross member of the rear fork. With the first hose guide mounted on the cross member, the second U-shaped portion is formed on the cross member.
According to the present invention, the piping structure is characterized in that a portion of the brake hose that is closer to the brake caliper than the second U-shaped portion is held by a second hose guide. The second hose guide limits the brake hose against movement in a direction perpendicular to the axis of the brake hose, but allows the brake hose to move in the axial direction of the brake hose. With the brake hose held by the second hose guide, the brake hose can easily be moved in the axial direction thereof.
According to the present invention, the piping structure is characterized in that the brake hose has a high flexural rigidity in a region extending from the portion held by the second hose guide toward the brake caliper. Further, the brake hose has a flexural rigidity, lower than the high flexural rigidity, in a region extending from the portion held by the second hose guide toward the master cylinder. For providing different flexural rigidities, material and/or structural differences may be introduced by using different materials and/or different outside diameters.
By increasing the flexural rigidity in the region extending toward the brake caliper, the wear resistance and fatigue strength of the brake hose positioned close to the rear wheel are increased. By making the flexural rigidity in the region extending toward the master cylinder lower than the flexural rigidity in the region extending toward the brake caliper, the second U-shaped portion can easily be formed, and the brake hose can easily be assembled.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.